Wave-signal responder system



Oct. 3, 1950 v w E 2,524,494

WAVE-SIGNAL RESPONDER SYSTEM Filed July 22, 1947 INVENTORS HUBERT WOOD RICHARD HARRIES DAVIES BY JAMES RENNIE WHITEHEAD ATTORNEY Patented Oct. 3, 1950 r 2,524,494

WAVE-SIGNAL RESPONDER SYSTEM Hubert Wood and Richard H. Davies, Hollinwood, and James Rennie Whitehead, London, Eng land, assignors to Ferranti Limited, Hollinwood, England, a corporation of Great Britain Application July 22, 1947, Serial No. 762,734

In Great Britain December 28, 1945 Section 1, Public Law 690, August 8, 1946 Patent expires December '28, 1965 4 Claims. (Cl. 250-- 15 2 a This invention relates to apparatus for use in quench frequency. The second form of responder wireless signalling systems of the kind in which is free from this disadvantage but has nevera transmitter having a receiver associated theretheless, in common with the previous form of with, is arranged to radiate a response signal in responder, certain other disadvantages. reply to an interrogation signal received by such 5 Firstly, owing to the sensitiveness of the superassociated receiver. regenerative receiver valve, random voltage fluc- More particularly the invention relates to such tuations or noise present in the receiving valve receiver/ transmitter devices, usually known as circuit when amplified and fed back to the grid responders of the type adapted for use with a of the transmitting valve, are likely to cause pulsed interrogating signal and is an improvetransmission of pulse signals in a form indisment in or modification of the responder, heretinguishable from that of the proper modified inafter referred to as a responder of the type signal pulses sent in response to an interrogating stated as described and claimed in an applicasignal.

tion of Hubert Wood, Richard H. Davies, and Secondly, another difiiculty presents itself James R. Whitehead, Serial No. 35,039/45, filed when either form of responder is employed in in Great Britain on December 28, 1945, entitled association with automatic ain t bi Improvements Relating to Radio Receivers of the m ans, that s t say, w th means f r main a n- Type Associated with Transmitting Means, and e e sens tiv y of he supe e e iv eassigned to the same assignee as the present iv r valv c nstant or n arly nstan as a application. One particular form of such re- 0 characteristic of the responder is altered. By a sponders as described in said prior patent applicharacteristic of the responder we mean, for cation is that in which reception of the interexample, thefrequency to which it is tuned, which rogating signal pulses is effected by means inmay be variable over a wide range, or the value eluding a super-regeneratively operated valve and of the, high-tension supply, or the aerial loading, in which a common tuned oscillatory circuit is which may vary with changing frequency or employed for both reception and subsequent rewith moisture deposition, An example of such transmission of response signals whereby the reautomatic gain stabilization means is set forth sponse is always sent at the same frequency as in an application of Hubert Wood et al., Serial that of interrogation. It is with this particular N0. 35,039/45, filed in Great Britain 011 mform that the present invention is concerned. h r 1945, l d p ov e s Relating to In one arrangement of this form of responder Radio Receivers Of he yp s a d W h of the type stated a single valve performs the T n mi n M ns, and a i n d o he am dual function of a super-regeneratively operated assignee as the Present pp amplifier for the reception of interrogating pulses The fea ure of an a o atic gain stabilization and, when supplied by way of a pulse widening means is the application to the receiving valve circuit with a suitable controlling potential deof a mp nsa p ial d rmin d by the rived from the received interrogating pulse sigandom v a fluctuations o s p s nals, as a transmitting oscillator. in the receiving valve when it is not receiving In another arrangement of the same general Signal p s that is o say, When it is in its form of responder of th t t t d, a doublenormal quiescent state. During the retransmistriode valve having a common cathode is emsion of a r p signal pulse the larger a p ployed for both the super-regenerative receiving tilde Oscillations p t In the common tuned valve and transmitting oscillator valve functions, circuit give rise o d C e W in the single the requisite quench oscillation being fed to the lv 0r do b er fle valv Co nected thereto control grid of one valve section and the output with the result that, after the retransmission 7 from the pulse-width controlling circuit being there is a heavy negative doea hode bias fed to the control grid of the other valve section. owing to th a c ed ch g s p ent on the The tuned circuit is again common to both valve condensers in the grid and cathode circuits. sections, being connected between their anodes S e e therefore must elapse before se and control grids. condensers can discharge through their associ- In the first-mentioned form the common single ated resistances sufliciently for the automatic valve is subject to the quench oscillation even gain stabilization means to restore the receivwhen functioning as an oscillator for retransmiting valve to the required sensitivity for normal ting the modified signal pulses, and thus the reception. It is not possible to reduce thetime transmitted response signal is modulated at the constants of these condenser circuits since the 3 width of the response pulse transmitted is also dependent on them. The frequency at which the interrogating pulses recur may be such that there is insufficient time for the automatic gain stabilization means to resume control between pulses, with the result that the responder may not operate satisfactorily.

The main object of the present invention is to provide a responder of the type and form stated which is free from the above disadvantages.

According to the present invention, a wavesignal responder comprises a super-regenerative circuit including a regenerator valve, means for maintaining the sensitivity of the super-regenerative circuit substantially constant as a characteristic of the responder system is altered, and a transmitting valve controlled by the received signal output of the super-regenerative circuit, the receiving valve and transmitting valve having a common oscillatory circuit connected between their control grids and anodes but each having separate and mutually independent cathode circuits.

One embodiment of the invention will now be described by way of example with reference to the accompanying drawing which shows a circuit arrangement of a responder of the type stated embodying the invention.

This embodiment comprises a super-regenerative radio receiver including a triode receiving valve I forming part of a Hartley-type oscillator, the cathode 2 of the valve being connected to the earthed negative pole of a high-tension supply by way of a biasing resistance 3 :and its radiofrequency decoupling condenser '5 and to the positive pole of the high-tension supply by way of a resistance 5 The aerial, not shown, is coupled by coil '5 to the inductance 6 of tuned circuit including variable condenser 5a. The mid-point ii of the inductance is connected to the positive pole of the high-tension supply.

.A quench-frequency oscillator is provided consisting of a triodevalve connected as a conventional feed-back nscillator. The high-potential end of inductance winding 8 of this oscillator is joined by way of a resistance 9, blocking condenser ill, and radio-frequency choke H to control grid 12 of valve l.

One end of the tuned circuit 6, be is connected by way of condenser i3 to control grid I? of valve I and by way of condenser E3 to the control grid i i of a triode transmitting valve if, the anode it of which is joined to the other end of tuned circuit 6., 6d. Cathode ll of valve 15 is connected to earth by way of :a biasing resistance I8 having a condenser 19 parallel therewith and to the positive pole of the high-tension supply by way of a resistance 55. The anode side of tuned circuit 5a is connected by way of condenser 20 to anode 2i of a diode detector valve 2 2, the oathode 23 of which is connected to earth. The anode and cathode of this diode valve are shunted by load resistance 25. Anode 2! of this diode valve is also connected by Way :of radio-frequency choke 25 to the control grid 26 of a pentode amplifier valve 2?. Cathode 5| of valve 21 is connected to earth through the parallel combination of biasing resistance 28 and decoupling condenser 29. Anode 3i] of valve 21 is joined to the positive pole of the high-tension supply by way of resistance 3| and is also connected by way of condenser 32 to the control grid 33 of a triode valve .34. Anode 35 of this valve is joined directly to the positive pole of the high-tension supply while cathode 36 isjoined to earth byway of a cathode-load resistance 37 and is further connected through a pulse-width controlling circuit, comprising condenser 39 and a parallel resistance 4|, and a radio-irequency'c'hoke 1 5 to control grid 14 of transmitting valve l5. A grid-leak resistance 42 is connected between control grid 33 and earth.

A connection is also made from anode 2| of diode valve 22 through a condenser 56 to control grid 51 of a pentode amplifier valve 58, a gridleak resistance being provided between such control grid and earth. Cathode 59 of valve 58 is connected to earth through an inductance Eil and a parallel condenser Bl while the anode 62 is joined to the positive pole of the high-tension supply by way of a load resistance 63. The circuit formed by inductance 60 and condenser BI is arranged to be resonant at the quench frequency. Anode B2 is also connected to cathode 64 of a diode rectifier valve 65 by way of condenser 66. cathode 64 being joined to the anode 61 of this diode through two serially connected resistances 6-8 and 69. The anode t! of diode valve -55 is also connected by Way of resistance H! to the control grid H of triode valve 12, the anode 13 of which is connected directly to the positive terminal of the high-tension supply. Anode 61 is also connected by way of condenser 14 to the junction of resistance 68 and 69 and to the cathode of valve 12, the latter electrode being also joined by way of condenser 1.6 to control grid 'il. Re sistances 69 and 70, together with condensers I4 and 1-6 form a smoothing circuit. Cathode I5 is also connected to earth by Way of a cathode-load resistance l l shunted by condenser 18 and is further joined by way of resistance I9 to the end of choke H remote from control grid 12 of triode valve I.

In operation, signalpulses transmitted from a ground or other remote interrogating station are picked up by an aerial, not shown, fed to tuned circuits 5, 5a, amplified super-regeneratively by valve I and are rectified by diode valve 22 and its associated components. The resulting rectified signals are amplified by pen-tode valve 22 and are then applied to the control grid circuit of valve 34. The positive polarity pulse output appearing across resistance 31 is modified insofar as its width is concerned by the pulse-width controlling circuit formed by condenser 39 and resistance -41, and appears in this modified form at the control grid 14 of transmitting valve i5. Valve l5 which is normally held in suppressed condition by the negative bias potential imposed on its control grid by the network 55, I8, is thereby caused to oscillate violently and cause retransmission of a response pulse signal.

During the intervals between reception of interrogating signal pulses, periods of radio-frequency oscillations due to the super-regenerative amplification of the random voltage fluctuations or noise in the current of valve I, and recurrent at the frequency of the quenching oscillations, are produced across load resistance 24. These oscillations, on being rectified by the diode r detector valve 22, deliver an output which comprises random voltage fluctuations, with a strong quench-frequency component having a random amplitude variation. This output :is employed to derive a potential for controlling the amount of regeneration within the super-regenerative ircuit of valve I by varying the grid-to-cathode bias of such valve in the following .manner.

The output fromdiode valve 22 is fed t pentode amplifier valve 58 by way of condenser 56 75 and the amplified output from this valve is taken from across its load resistance 63. This output has no strong quench-frequency component W- ing to the degenerative feed-back eifect of the tuned rejector circuit 60, 6| in its cathode lead. This output is then transferred as an input potential to diode rectifier valve 65. The rectified output from this valve develops a mean direct current in load resistance 69 and the resulting potential across this resistance, which is proportional to the mean amplitude of the random voltage fluctuations, is smoothed by the smoothing circuit formed by resistance 10 and condensers 14 and I6 and is fed as a negative bias potential to control grid H of triode valve 12. This potential is not suflicient to bias the valve beyond its cut-on value. A varying potential is accordingly developed across resistance 11 and this is transferred by way of resistance 19 and choke I I to the control grid I2 of valve I of the superregenerative receiving stage as a varying positive potential.

If now the super-regenerative receiver becomes more sensitive, for instance, consequent upon a change in the tuning frequency, the noise oscillations produced across load resistance 69 increase. Consequently, control grid H of valve 12 becomes more negative and the potential across cathode load resistance 11 is decreased, thereby reducing the positive potential applied to control grid I2 of valve I which, in turn, leads to a decrease in the amount of regeneration and hence the amplitude of the noise oscillations produced by such super-regenerative receiving stage. Hence it will be seen that the sensitivity of the latter stage is reduced to its original value. Adequate compensation is provided since the values of the components associated with valves 58, 65 and 12 are suitabl chosen to provide sufficient gain.

It will be seen that the transmitted pulse is not modulated at the frequency of the quench oscillations since those oscillations are not applied to transmitting valve I5 because condensers I3, I3 together with the lower half of inductance 6 comprise a filter which does not pass quenchfrequency potentials. Further it will be seen that by making the cathode circuit of receiving valve I independent of that of the transmitting valve I 5, the condenser may be made of sufilciently small capacity to provide a short time constant in the cathode circuit of valve I5 thereby permitting the receiving valve quickly to return to its normal quiescent state after transmission of a response signal with consequent efllcient stabilization while, at the same time, the condenser I9 of the transmitting valve cathode circuit may be made adequately large for the purpose of enhancing the width of the modified pulse.

Resistance 54 ensures that cathode 2 of valve I 1s maintained at the requisite positive potential with respect to grid I 2 When the valve is operating under normal receiving conditions while permitting a relatively low value of resistance 3- for the purpose of shortening the time constant of the network 3, 4 to the required value. Resistance 55 serves a somewhat similar purpose with regard to valve I 5, which is by this means, by maintaining the control grid of such valveat or beyond its cut-off value except when a positive potential is applied thereto from the valve 34, prevented from transmitting signals caused by random voltage fluctuations.

While there has been described what is at present considered to be the preferred embodiment of this invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention, and it is, therefore, aimed to cover all such changes and modifications as fall within the true spirit and scope of the invention.

What is claimed is:

1. A wave-signal responder system comprising, a superregenerative circuit including a regenerator valve, means for maintaining the sensitivity of said circuit substantially constant as a characteristic of the responder system is altered, and a transmitting valve controlled by the received signal output of said superregenerative circuit, said regenerator valve and said transmitting valve having. a common oscillatory circuit connected between their control grids and anodes but each having separate and mutually independent cathode circuits,

2. A responder as claimed in claim 1 in which the cathode circuits of each of said receiving and transmitting valves comprise a resistance and a parallel condenser, the time constant of the oathode circuit of said receiving valve having a value selected to ensure rapid recovery of such valve to its normal quiescent condition after the transmission of each response pulse and the time constant of the cathode circuit of said transmitting valve having a value selected to provide a desired value v of pulse duration of the response pulses ,transmitted by said transmitting valve.

3. A responder as claimed inclaimlin which said common oscillatory circuit comprises a parallel inductance and capacity network connected directly at one end'to the anodes of each of said receiving and transmitting valves and connected at its other end to the control grids of each of said valves by way of separate blocking condensers, the values of said blocking condensers being such that in conjunction with said inductance they constitute a filter network to prevent the transmission of quenching-frequency oscillations from said receiving-valve control grid to said transmitting-valve control grid.

4. A responder as claimed in claim 3 in which said inductance is tapped intermediate its ends and connected therefrom to the positive terminal of a high-tension supply source.

HUBERT WOOD. RICHARD H. DAVIES. JAMES RENNIE WHITEHEAD.

REFERENCES CITED UNITED STATES PATENTS Number Name Date 2,414,992 Wheeler Jan. 28, 1947 2,415,667 Wheeler ...Feb. 11, 1947 2,429,513 Hansen et al. Oct. 21, 1947 

